JPH0684622A - Radio wave absorber - Google Patents

Abstract

PURPOSE:To realize a magnetic material excellent in radio wave absorbing characteristics in which reflection coefficient can be kept high over a wide frequency region by adding specified quantities of titanium dioxide, vanadium pentaoxide, and hafnium oxide. CONSTITUTION:Zinc oxide ZnO, nickel monoxide NiO, and copper monoxide CuO are contained as main constituents while ferric oxide Fe2O3 is contained as the remainder and one or both of silicon dioxide SiO2 and manganese monoxide MnO is further contained as subconstituent. Furthermore titanium dioxide TiO2, vanadium pentaoxide V2O5 and hafnium oxide are contained, respectively, upto 0.30wt.%, 0.20wt.% and 1.00wt.% as additives. This composition provides an oxide magnetic material for absorbing radio wave having significantly improved radio wave absorbing characteristics in which the region where the value of radio wave reflection coefficient is lower than -20dB is widened in the frequency region higher than 400MHz and low dielectric constant is achieved.

Description

Detailed Description of the Invention

[0001]

This invention is used in an anechoic chamber.
A Ni-Cu-Zn-based oxide magnetic material used as a material for a ferrite electromagnetic wave absorber, which is used in a frequency range of 0 to 1000 MHz, and particularly 32.0 to 3 as a main component.
5.0 mol% zinc oxide (hereinafter referred to as ZnO), 1
0.0-12.0 mol% nickel monoxide (Ni
O), 5.0 to 7.0 mol% of copper monoxide (CuO),
And the balance ferric oxide (Fe ₂ O ₃ ), and 0.05 wt% or less of silicon dioxide (SiO ₂ ) as a subcomponent and 0.
The present invention relates to an improvement of an oxide magnetic material for radio wave absorbers containing one or two components of manganese monoxide (MnO) of 10 wt% or less.

[0002]

2. Description of the Related Art Conventionally, in the case of manufacturing this kind of ferrite electromagnetic wave absorber, zinc oxide (ZnO), nickel monoxide (NiO), copper monoxide (CuO), and ferric oxide ( Fe ₂ O ₃ ) powder and an auxiliary component of 0.0
5 wt% or less of silicon dioxide (SiO ₂ ), 0.10 wt
% Or less of one or two kinds of manganese monoxide (MnO) powder, and after molding and molding, 1050 ° C. to 1 in an air atmosphere.
A Ni—Cu—Zn-based oxide magnetic material sintered body was obtained by holding the material in the temperature range of 170 ° C. for about 2 hours and performing sintering.

[0003]

When the sintered body obtained as described above is attached to the inner wall of the anechoic chamber, the frequency range where the reflection coefficient is -20 dB or less is 50 to 4 even when the thickness is adjusted.
It is 00 MHz. Therefore, the urethane absorber is used in the frequency region of 400 MHz or higher. However, if the number of urethane absorbers is increased until they are aligned, the length thereof becomes large, which makes it difficult to use.

Therefore, the present invention is to provide a magnetic material having a good electromagnetic wave absorption property, which can maintain the reflection coefficient of -20 dB or less in a wide frequency range of about 500 MHz or more with only a sintered body of an oxide magnetic material. It is what

[0005]

The radio wave absorber of the present invention comprises:
32.0 to 35.0 mol% zinc oxide (ZnO) as a main component, 10.0 to 12.0 mol% nickel monoxide (NiO), 5.0 to 7.0 mol% copper monoxide (CuO), And the balance of ferric oxide (Fe ₂ O ₃ ), and 0.05 wt% or less (not including 0.0 wt%) of silicon dioxide (SiO ₂ ) as a sub-component, 0.10 wt% or less (0.0 wt%) Manganese monoxide (Mn not included)
O) in the oxide magnetic material for a radio wave absorber containing one or two components respectively, titanium dioxide (TiO ₂ ) of 0.30 wt% or less (not including 0.0%), 0.20 wt%
The following (not including 0.0 wt%) vanadium pentoxide (V
₂ O ₅ ) and hafnium oxide (HfO ₂ ) of 1.00 wt% or less (not including 0.0 wt%) as additives.

[0006]

The additives V ₂ O ₅ and HfO ₂ are precipitated in the grain boundaries respectively by holding the additives V ₂ O ₅ and HfO ₂ in the atmosphere in the temperature range of 1050 ° C. to 1170 ° C. for 2 hours and sintering. It is thought that the additive TiO ₂ is used as a solid solution in the crystal by the above-mentioned sintering treatment to increase the resistivity inside the crystal and further to make the crystal structure uniform. . Ni-Cu- containing these three additives
In addition to the effect of the sub-components described above, the Zn-based oxide magnetic material has a uniform electromagnetic property inside the tissue, has a wide frequency range with a reflection coefficient of -20 dB or less, and exhibits a low dielectric constant value. it is conceivable that.

[0007]

[Examples] The details of the experiments of Examples and Comparative Examples of the present invention will be described below. As a standard main component of an oxide magnetic material obtained by mixing, molding and firing oxide powder, 50.
0 mol% of ferric oxide (Fe ₂ O _3), 32.0mo
1% zinc oxide (ZnO), 12.0 mol% nickel oxide (NiO), and 6.0 mol% copper monoxide (C).
uO) and, as secondary components, 0.05% by weight or less of silicon dioxide (SiO ₂ ) and 0.10% by weight or less of manganese monoxide (MnO).
Cu-Zn oxide magnetic material, titanium dioxide (TiO 2
₂ ), vanadium pentoxide (V ₂ O ₅ ), and hafnium oxide (HfO ₂ ) are added in various proportions in a combined manner to form a plurality of Ni-Cu-Zn-based oxide magnetic materials of the first embodiment. Various prototypes were manufactured, and as a standard comparative example, a conventional Ni-Cu-Zn-based oxide magnetic material without the addition of the above additives,
As a first comparative example, a plurality of Ni—Cu—Zn-based oxide magnetic materials to which the above additives were added alone or in combination were manufactured.

In the trial production of these examples and comparative examples, a predetermined amount of each oxide raw material was weighed, mixed, pre-baked, granulated, and after molding and pressing, 110 in the atmosphere.
It was calcined at 0 ° C. for 2 hours. The reflection coefficient of radio waves of each frequency was measured by the coaxial tube method for each material having a different composition with an outer diameter of 19.8 mm, an inner diameter of 8.6 mm.

Table 1 below shows the sample No. of the first embodiment that was prototyped. 8-10, No. 12, 13, 15, 16 and sample No. 1 as a standard comparative example. 1 and sample No. 1 as a first comparative example. 2-7, No. About 11, 14, 17 and
The content and reflection coefficient of each subcomponent and additive is -2.
It shows the range of the frequency region of 0 dB or less.

[0010]

[Table 1]

According to Table 1, the dielectric constant of the conventional standard comparative example is increased by the combined addition of titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ) and hafnium oxide (HfO ₂ ) which are additives. Sample No. Lower than 1, the reflection coefficient (-
It can be seen that the range of the frequency region of 20 dB or less) is wider. Of the above three additives, TiO ₂ and H
fO ₂ precipitates at the grain boundaries of the Ni—Cu—Zn-based oxide magnetic material to increase the resistivity of the grain boundaries, and V ₂ O ₅ forms a solid solution in the crystals to increase the resistivity in the crystals and the crystals. It is considered to be effective for tissue homogenization, and the electromagnetic effect inside the tissue is homogenized by these combined actions, the resistivity of the whole tissue is increased, and the frequency range of the reflection coefficient (-20 dB or less) is widened. it is conceivable that.

In Table 1, 0.40 wt% of TiO ₂ is added.
Added sample No. 11, sample No. 11 to which 0.30 wt% of V ₂ O ₅ was added. 14, and 1.10 wt% of HfO _2.
Added sample No. In No. 17, it is considered that abnormal grain growth was observed, which resulted in increased power loss and dielectric constant. Further, the sample No. It is understood that 2 to 7 each have 0.0% of the additive alone or two of them, and in this case as well, the power loss and the dielectric constant are large and the effect is small.

Table 2 below shows sample N of the conventional standard comparative example.
o. 1 and the sample No. 1 of the embodiment of the present invention. 8 to 17, the relationship between the amount of each additive added and the reflection coefficient at each frequency is shown.

[0014]

[Table 2]

According to Table 2, titanium dioxide (TiO ₂ )
As the addition amount of is increased, the value of the reflection coefficient of the radio wave is increased in the low frequency range and the absorption characteristics of the radio wave is improved, but it tends to be deteriorated in the high frequency range. When 0.30 wt% of titanium dioxide (TiO) is added, the reflection coefficient is -2 at 500 MHz.
A value of 0 dB was obtained, and a reflection coefficient at 50 MHz was -30.1 dB, which was superior to the conventional additive-free product, and an oxide magnetic material for a radio wave absorber was obtained.

As the added amount of vanadium pentoxide (V ₂ O ₅ ) and hafnium oxide (HfO ₂ ) is increased, the value of the reflection coefficient of the radio wave is increased in a high frequency range, and the material has excellent radio wave absorption characteristics. However, in the low frequency range, the value of the reflection coefficient of the radio wave becomes large and the deterioration tendency is seen. Vanadium pentoxide (V ₂ O ₅ ) 0.
When 20 wt% is added and hafnium oxide (HfO ₂ )
When 1.00 wt% was added, an oxide magnetic material for a wave absorber superior to the conventional non-added product was obtained.

The value of the reflection coefficient showing the electromagnetic wave absorption characteristics becomes large at around 50 MHz as the amount of titanium dioxide (TiO) added increases, and the frequency at which the reflection coefficient becomes maximum shifts to a lower frequency. Is shown. The shift of the frequency at which the reflection coefficient is maximum at these characteristic values corresponds to the value of the dielectric constant shown in Table 1, and is the maximum at the titanium dioxide (TiO ₂ ) additive composition having the minimum dielectric constant. The highest frequency is shown as the value showing the value of the reflection coefficient and the maximum reflection coefficient.

Further, if the addition amounts of vanadium pentoxide (V ₂ O ₅ ) and hafnium oxide (HfO ₂ ) are increased, it becomes 500 MHz.
The value of the reflection coefficient in the vicinity increases, and the frequency at which the reflection coefficient becomes maximum shows a result of shifting to a higher frequency. The shift of the frequency at which the reflection coefficient becomes maximum at these characteristic values matches the value of the dielectric constant shown in Table 1, and vanadium pentoxide (V ₂ O ₅ ) and hafnium oxide (HfO) at which the dielectric constant shows the minimum value. _In the additive composition of ₂ ), the highest reflection coefficient and the highest frequency are shown.

[0019]

According to the present invention, conventional nickel, copper,
0.30wt% or less (0.0w
titanium dioxide containing not) a t% (TiO _2), 0.20
Vanadium pentoxide (V ₂ O ₅ ) of wt% or less (not including 0.0 wt%), and 1.00 wt% or less (0.0 wt%)
% Of hafnium oxide (HfO ₂ ) is added, the value of the reflection coefficient of the radio wave is 400 MH compared with the conventional nickel, copper, zinc, and iron oxide magnetic materials.
In the frequency range of z or more, the range of -20 dB or less was widened, and an oxide magnetic material for a radio wave absorber having a significantly improved radio wave absorption characteristic was obtained.

Therefore, when the oxide magnetic material for a radio wave absorber according to the present invention is used, it can be applied to a radio wave absorber having a wider band, and a small anechoic chamber can be constructed at a low price.

[Brief description of drawings]

FIG. 1 shows a titanium dioxide (T) of a radio wave absorber according to the present invention.
iO ₂ ) is added in an amount of 0.0 wt% (comparative example), 0.1
The characteristic view which shows the relationship between the frequency and the reflection coefficient in 30MHz-600MHz range in case of 0 wt%, 0.30 wt%, and 0.40 wt%.

FIG. 2 shows the radio wave absorber according to the present invention in which vanadium pentoxide (V ₂ O ₅ ) was added in an amount of 0.0 wt% (comparative example), 0.
The characteristic view which shows the relationship between the frequency and the reflection coefficient in 30MHz-600MHz range in case of 10 wt%, 0.20 wt%, and 0.30 wt%.

FIG. 3 is a radio wave absorber according to the present invention in which the amount of hafnium oxide (HfO ₂ ) added is 0.0 wt% (comparative example);
The characteristic view which shows the relationship between the frequency and the reflection coefficient in 30MHz-600MHz range in case of 80 wt%, 1.00 wt%, and 1.10 wt%.

Claims (1)

[Claims] 1. A main component of 32.0 to 35.0 mol
% Zinc oxide (ZnO), 10.0-12.0 mol%
Nickel monoxide (NiO), 5.0-7.0 mol%
Copper monoxide (CuO), and the balance ferric oxide (Fe ₂ O)
₃ ) and contains 0.05 wt% or less (0.0
(not including wt%) silicon dioxide (SiO ₂ ), 0.10
0.30 wt% or less (0.0%) in an oxide magnetic material for a radio wave absorber containing one or two components of manganese monoxide (MnO) of not more than wt% (not including 0.0 wt%), respectively. Titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ) 0.20 wt% or less (not including 0.0 wt%) and 1.00
A radio wave absorber comprising hafnium oxide (HfO ₂ ) in an amount of wt% or less (not including 0.0 wt%) as an additive.